1. Field of the Invention
The invention generally relates to methods of manufacturing color filters and associated liquid crystal display (LCD) devices.
2. The Prior Art
In general, a monochrome or a color LCD device has the advantages of thinness, light weight and low power consumption. For this reason, LCD devices are widely used in various types of electronic equipment, from pocket calculators to large-scale office automation equipment.
Conventionally, a color LCD device includes a color filter at a position opposite to a liquid crystal layer. The color filter has three kinds of color (red, green and blue—RGB) resins separated by a black matrix having a plurality of apertures. The visibility of the LCD device mainly depends upon the characteristics of the black matrix of the color filter.
The basic structure of a conventional color filter is shown in FIG. 4. The color filter 20 includes a transparent substrate 24 with a black matrix 23 deposited thereon, the black matrix 23 defining a plurality of apertures (not labeled) therein. RGB color resins 22 are filled in the apertures of the black matrix 23 in a sequential repeating pattern. The RGB color resins 22 filter light beams passing therethrough, thus producing respective RGB color light beams.
The black matrix 23 functions as a light-shielding mask, to improve the contrast ratio of an LCD device using the color filter 20. In particular, the black matrix 23 increases the OD (Optical Density, i.e. light-shielding) value, and reduces optical reflectivity of the top and bottom surfaces thereof. However, the black matrix 23 is conventionally made from a metal whose optical reflectivity is too high, or is made from a resin whose OD value is too low. Thus, modified color filters have been developed to solve the above-described problems.
Referring to FIG. 5, a color filter as described in U.S. Pat. No. 6,285,424 issued on Sep. 4, 2001 is illustrated. The color filter 1 comprises a black matrix 9 formed on a transparent substrate 2. The black matrix 9 comprises a first antireflection film 3, a second antireflection film 4 and a metal screening film 5 formed one on top of the other in that order. The antireflection films 3, 4 are made of different kinds of metallic compounds having mutually different compositions. At least one of the films 3, 4, 5 contains chromium (Cr). In addition, RGB color resins are separately filled in apertures of the black matrix 9. A protective layer 6 and a conductive layer 7 are sequentially formed on the RGB color resins and the black matrix 9. The protective layer 6 functions as a layer flattening the color filter 1, and as an insulator.
In manufacturing of the color filter 1, firstly, the black matrix 9 having a plurality of apertures is formed on the transparent substrate 2 using exposing and developing technology. Then the RGB color resins are repeatedly and respectively filled in the apertures of the black matrix 9, so that every three adjacent apertures have three different color resins and cooperatively define a pixel. Then the protective layer 6 is formed on the RGB color resins and the black matrix 9, to provide an even outer surface for the color filter 1.
The multi-layer antireflection structure of the black matrix 9 can decrease the optical reflectivity of the surface thereof adjacent the transparent substrate 2. However, the optical reflectivity of the other surface thereof opposite to the transparent substrate 2 is still generally too great. That is, the optical reflectivity of the outer surface of the metal screening film 5 is too great. When the black matrix 9 is used in an LCD device, back light beams are reflected by the outer surface of the metal screening film 5 to an excessive degree. This creates light interference, which reduces the visibility of the LCD device.
Therefore, it is desired to obtain a color filter with low reflectivity on both surfaces thereof, and to obtain an LCD device incorporating such color filter.